Heating pad



A. S. KNAPP July 24, 1934.

HEAT ING PAD Filed Jan. 18, 1932 Peienied July 24, 1934 1,967,674

UNITED STATES PATENT OFFICE- HEATING PAD Andrew S. Knapp, Belleville, lll., assignor to Knapp-Monarch Company, Belleville, IIL, a corporation oi' Missouri Application January 18, 1932, Serial No. 587,297

3 Claims. (Cl. 21S-46) An object of my present invention is to provide Figure 5 shows the parts of Figure 4 in partially a heating pad so constructed that all danger assembled position. of nre as caused by contact between different On the accompanying drawing, I have used portions ci the heating element, or twisting of the reference character A to indicate generally 5 the heating element, is entirely eliminated and a heating pad and the character B to indicate 60 yet the pad is of simple, durable and inexpensive a current supply cord therefor. A switch is shown construction. at for controlling the flow of current to the More particularly, it is my object to provide heating pad A.. insulation between the heating element and the The heating pad A comprises a pair of heating 10 cover oi a heating pad, which consists of an elements 12, an asbestos envelope C and a lex- 55 envelope of asbestos having suiiicient exibility ible cloth covering 14 together with associated to withstand the ordinary usage tc which a heatparts such as a control thermostat 16 and coning pad is put without breaking the iibres thereof nectors 18. The heating element 12 is usually completely enclosing or housing the heating elemade in the form of a cord of asbestos around ment so that any short circuit 'between diierent which a resistance Wire is wrapped with an as- 70 portions of the heating element and the resultant bestos covering over the resistance wire, or the arc caused thereby will not burn the cover of resistance Wire embedded in the asbestos cordthe heating pad and the user thereof, but will like core. A heating element of this character be confined within the asbestos envelope and is usually secured to a cloth backing in the 20 cannot cause any damage because both the enordinary type of heating pad and then covered 75 velope and the heating element itself are non- -with cloth which is usually of inammable charinilammable. acter. In my heating pad construction, how- A further object is to'provide a heating pad ever, the heating element 12 is secured to a sheet construction consisting of a ilexible cloth cover o i asbestos 20 by sewing it thereon with threads g5 formed of blanket material or the like whereby 22. The sheet of asbestos 20 is a woven asbestos 30 to give the heating pad a desirable outer surface cloth so as to make it entirely ilexible and thereand a heating element which is entirely and by suitable for use in heating pad constructions. completely inclosed in an insulating envelope The asbestos sheet 20 together with a similar such as one formed of asbestos cloth arranged asbestos sheet 24- forms the en'3lope hereinbeto eliminate all openings through which the heatfore referred to as C. 35

ing element might mechanically and/or electri- The thermostat 16 and the connectors 18 procally contact with the cover for the pad. vide for automatic control-of the heating o1' the Still a further object is to provide the enheating pad and for connection with the supply velope in the form of two sheets of asbestos, the cord B, respectively. The edges of the sheets 20 edges of which are sewed or otherwise secured and 24' are indicated as a, b, c and d. As shown 90 together to completely enclose the heating elein Figure 3, the edges a are sewed together by ment and thus prevent contact betweenit and stitches 26. The edges c are sewed together by the cover for the pad. stitches 28. As shown in Figure 4, the edges d With these and other objects in view my inare sewed together by Stitches 30 and the edges vention consists in the construction, arrangement b are SeWed together by Stitches 32- The Stitches 95 and combination of the various parts of my 28- 30 and 32 also Sew tile edges Uf the 010th device, whereby the objects contemplated are at- 'Covering 14 methel Instead 0f the Stitches 23,

tained, eenereineiier more fully setformpointed the Sheets 20 and 24 may be combined 01 made out in m laims; nd illustrated in the ccomin one she@ folded ab this point" pamng grim, ig which: a The entire heating pad construction is sewed 100 together inside-out as indicated in Figure 5, the

me 1 iigmgegsgg View of a heatmg right hond side or which is sewed together end Fi bod; i a se grated er ti vi f the left hand side of which is not yet sewed.

eure S p P Spe "e ew 0 After being sewed together with the exception the sides o1' the asbestos envelope for the heating of a part indicated at 34 in Figure 1 the pad of 105 element and the heating element secured to one Figure 5 is turned insidemut to apper as shown 0f the SideS- in Figures 3 and 4 the openin g indicated at 34 Figures 3 and 4 are Sectional views 0n lmes being provided i'or the parte to be reversed 3-3 and 4-4, respectweiy. Gf Figure 1 Showing through. Stitches 36 are then used to close the the construction of the heating pad; and opening 34. 110

By the foregoing construction it will be obvious that the heating element 22 is completely enclosed in the non-le envelope C, this being best illustrated in Figures 3 and 4 in which all four edges, a, b, c and d, are illustrated as being sewed together. There is no chance for a fire occurring on account of dinerent portions oi the heating element contacting with each other and then being separated and forming an arc. Even though such arc is formed it cannot burn the cloth cover 14 because of the asbestos sheets 20 and 24 interposed between the element and the cloth. There is not even any possibility of contact between the heating element and the cloth at the edges of the asbestos sheets 20 and 24 because they are sewed together to completely house the heating element as already described.

Although throughout the specification I have used the term asbestos to define the sheets 20 and 24, it is obvious that other insulating materials which are suflciently flexible but which are non-inflammable and non-conductive of electricity could be used instead. I have used asbestes because it is a good insulator and in woven form is sufficiently ilexihle for use as described.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my'invention, and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents, which may be reasonably included within their scope.

I claim as my invention:

1. In an electric heating pad, the combination of an electric heating element, an outside cover therefor formed of flexible cloth and means for insulating said heating element from said cover to prevent contact of the heating element with the cover, yet allowing free conformation of the heating pad to any shape desired, said means comprising a fire resisting envelope of cloth-like formation having sufncient flexibility to permit ordinary use without the materials thereof being broken, said re resisting envelope completely enclosing said heating element and positioned Within said cover and having said heating element secured thereto whereby the different parts of the heating element are maintained in spaced position relative to each other, said fire resisting envelope preventing an arc caused by a short circuit of said heating element burning said cover.

2. In an electric heating pad, the combination of an electric heating element, an outside cover therefor formed of flexible cloth and means for insulating said heating element from said cover to prevent contact of the heating element with the cover, yet allowing free conformation of the heating pad to any shape desired, said means comprising a nre resisting envelope of cloth-like formation having sufiicient flexibility to permit ordinaryuse without the materials thereof being broken and preventing any fire caused by a short circuit of said heating element burning mid cover.

3. In an electric heating pad, the combination of an electric heating element, an outside cover therefor formed of flexible cloth and means for insulating said heating element from said cover side cover.

ANDREW S. KNAPP. 

